Pakistani policemen inspect the site of a bomb explosion in Islamabad on April 3, 2014. Pakistan's former military ruler Pervez Musharraf, who is on trial for treason, escaped the bomb blast in the early hours, police said. The bomb was planted on his route from an army hospital where he has been staying since January to his home on the outskirts of Islamabad. AFP PHOTO/Aamir QURESHIAAMIR QURESHI/AFP/Getty Images

A bomb apparently directed at Pervez Musharraf, the former Pakistani military ruler, went off early Thursday, minutes after his convoy had passed a traffic intersection in Islamabad, the capital, police officials said.

The bomb went off as Musharraf was secretly being shifted from a military hospital in neighboring Rawalpindi to his farmhouse on the outskirts of Islamabad.

The blast did not cause any casualties to Musharraf's security convoy, police officials said. But the explosion left a foot-deep crater on a sidewalk near a busy traffic intersection on the boundary line between Rawalpindi and Islamabad.

"The explosion occurred after Musharraf's convoy had passed," said Pervaiz Rashid, the Pakistani information minister. "Investigations are under way."

Musharraf, who has been charged with treason, was admitted Jan. 2 to the Armed Forces Institute of Cardiology after he complained of sudden heart trouble while he was on the way to attend his trial.

On Monday, Musharraf was formally indicted in the treason trial, an unprecedented development in the country's history. No military ruler has ever been tried on treason charges or on other counts of abuse of power. The powerful military has traditionally maintained an overarching influence over the civilian government.

Musharraf is accused of subverting the constitution in 2007 when he fired top members of the judiciary to stem a growing opposition movement. But the move backfired as Musharraf's political party lost the 2008 national elections in a thumping defeat. Musharraf later resigned, under the threat of impeachment, opting for self-imposed exile in London and Dubai.

In 2013, Musharraf returned to the country to revive his political fortunes and participate in general elections. But he was barred from taking part in the elections by the courts, and his political party, All Pakistan Muslim League, failed to gain traction.